Electrostatic filters are well known in the art both for home and industrial use. Such filters typically employ wires astride the air path where the wires are maintained at a high potential designed to attract particles in the air. The filters are used along with mechanical filters designed to trap particles of relatively gross size earlier in the air stream. Filter systems of this type are found in many forced air systems for home use and in clean rooms used for example in semiconductor manufacture.
Particularly for use in the semiconductor industry, the demand for systems which remove smaller and smaller particles from the air is acute. This requirement arises from the fact that integrated circuits with smaller and smaller feature size suffer significant damage from air borne contaminants of smaller and smaller size. These contaminants decrease yields of semiconductor devices and thus increase costs. It is well known that the elimination of smaller and smaller air borne particles is a major concern of the semiconductor industry.
The approach to eliminating smaller and smaller particles is to employ better mechanical filters and stronger electric fields. But such means obstruct the air flow and result in an increased kinetic energy for the particles. This, in turn, reduces the effectiveness of the mechanical filter and the fields. One particularly effective mechanical filter, the HEPA filter, has a corrugated cross section exposing a relatively large area of filter material to air borne particles without excessive obstruction of the air path. Such filters are of the type used in car air filters. But even these filters increase the kinetic energy of air borne particles enough such that trapping of particles on the order of microns in diameter is achieved only with very elaborate and costly systems.